Microsoft usually announces the new games for the Xbox Game Pass at the start of the month. But, for some reason - which may or may not have something to do with the unconfirmed Xbox Developer Direct showcase - Microsoft took its sweet time announcing the games for the month. We're nearly halfway through Janus' namesake month and we just caught wind of the Game Pass' opening salvo. If it makes a difference, Xbox slid in a couple of games unannounced, so there goes the answer of why you saw Stranded Deep and Mortal Shell: Enhanced Edition pop up for some reason.
The highlight of the Game Pass this month is three JRPGs. The first two, Persona 4 Golden and Persona 3 Portable, are coming on the 19th. Then, the other one, Monster Hunter Rise, will be available the day after on the 20th.
Persona 3 Portable and Persona 4 Golden are part of the trio of top-billing Persona games that was announced last year. Persona 5 Royal is already available on the Game Pass, so the new additions should make it easy for you to backtrack and play the predecessors. It's worth noting that Persona 3 Portable is a launch title as it will be available on both the Nintendo Switch, the PS4, and the PC on the same day as well.